Category
General Spine
Sang Yoon Kim
Myung Jun Shin
Purpose
To investigate the morphology of posterior-dura-mater (PDM) and to assess the difference of findings between the groups of isthmic and degenerative spondylolisthesis on midline-sagittal-T1WI of the L-spine MRI.
Materials & Methods
Midline-sagittal-T1WI were retrospectively reviewed for 150 patients (50 without spondylolisthesis, 50 with isthmic spondylolisthesis, 50 with degenerative spondylolisthesis). We named the morphologic finding of PDM with wavy and anterior bulging contour, as “posterior-dural-tenting-sign” and investigated the conditions showing this sign.
Results
In 36 of 50 cases without spondylolisthesis, PDM was focally anchored at conjoining area of both vertebral laminae in all levels. In 14, PDM was not anchored and detached from the anchoring point at L4 (3 cases) & L5 (11 cases). And in 39 cases, the morphology of PDM was smooth-flat without tenting in all levels. In 11 cases, tenting sign was positive (3 due to epidural lipomatosis, 6 due to anterior bulging of interspinous ligament, 2 without significant cause). In 33 of 50 cases with isthmic spondylolisthesis, tenting sign was positive. And in 17 cases, tenting sign was negative (in 12 PDM was detached from the anchoring point, in 5 tenting sign was minimal). In 33 of 50 cases with degenerative spondylolisthesis, tenting sign was negative. And in 17 cases, tenting sign was positive (14 due to anterior bulging of interspinous ligament, 1 due to epidural lipomatosis, 2 without significant cause).
Conclusion
The tenting-sign could be seen in the condition with epidural lipomatosis and anterior bulging of interspinous ligament, even though there is no spondylolisthesis. And it was frequently seen in isthmic spondylolisthesis than degenerative spondylolisthesis, statistically. So, posterior-dural-tenting-sign could be an useful sign in distinguishing isthmic spondylolisthesis from degenerative spondylolisthesis.
References
Borré DG, Borré GE, Aude F, Palmieri GN. Lumbosacral epidural lipomatosis: MRI grading. Eur Radiol. 2003;13:1709–1721. doi: 10.1007/s00330-002-1716-4.